从 JApplet 更改为 JFrame

Question

所以我有这段代码可以在 Java 中创建一个计算器。但它是用 JApplet 制作的，我需要它与 JFrame 一起使用。需要改什么？

import javax.swing.*;
import javax.swing.JOptionPane;
import java.awt.*;
import java.awt.event.*;

public class Calculator extends JApplet {
   public void init() {
      CalculatorPanel calc=new CalculatorPanel();
      getContentPane().add(calc);
      }
   }

   class CalculatorPanel extends JPanel implements ActionListener {
      JButton 
n1,n2,n3,n4,n5,n6,n7,n8,n9,n0,plus,minus,mul,div,dot,equal;
      static JTextField result=new JTextField("0",45);
      static String lastCommand=null;
      JOptionPane p=new JOptionPane();
      double preRes=0,secVal=0,res;

      private static void assign(String no)
        {
         if((result.getText()).equals("0"))
            result.setText(no);
          else if(lastCommand=="=")
           {
            result.setText(no);
            lastCommand=null;
           }
          else
            result.setText(result.getText()+no);
         }

      public CalculatorPanel() {
         setLayout(new BorderLayout());
         result.setEditable(false);
         result.setSize(300,200);
         add(result,BorderLayout.NORTH);
         JPanel panel=new JPanel();
         panel.setLayout(new GridLayout(4,4));

         n7=new JButton("7");
         panel.add(n7);
         n7.addActionListener(this);
         n8=new JButton("8");
         panel.add(n8);
         n8.addActionListener(this);
         n9=new JButton("9");
         panel.add(n9);
         n9.addActionListener(this);
         div=new JButton("/");
         panel.add(div);
         div.addActionListener(this);

         n4=new JButton("4");
         panel.add(n4);
         n4.addActionListener(this);
         n5=new JButton("5");
         panel.add(n5);
         n5.addActionListener(this);
         n6=new JButton("6");
         panel.add(n6);
         n6.addActionListener(this);
         mul=new JButton("*");
         panel.add(mul);
         mul.addActionListener(this);

         n1=new JButton("1");
         panel.add(n1);
         n1.addActionListener(this);
         n2=new JButton("2");
         panel.add(n2);
         n2.addActionListener(this);
         n3=new JButton("3");
         panel.add(n3);
         n3.addActionListener(this);
         minus=new JButton("-");
         panel.add(minus);
         minus.addActionListener(this);

         dot=new JButton(".");
         panel.add(dot);
         dot.addActionListener(this);
         n0=new JButton("0");
         panel.add(n0);
         n0.addActionListener(this);
         equal=new JButton("=");
         panel.add(equal);
         equal.addActionListener(this);
         plus=new JButton("+");
         panel.add(plus);
         plus.addActionListener(this);
         add(panel,BorderLayout.CENTER);
      }
      public void actionPerformed(ActionEvent ae)
         {
      if(ae.getSource()==n1) assign("1");
      else if(ae.getSource()==n2) assign("2");
      else if(ae.getSource()==n3) assign("3");
      else if(ae.getSource()==n4) assign("4");
      else if(ae.getSource()==n5) assign("5");
      else if(ae.getSource()==n6) assign("6");
      else if(ae.getSource()==n7) assign("7");
      else if(ae.getSource()==n8) assign("8");
      else if(ae.getSource()==n9) assign("9");
      else if(ae.getSource()==n0) assign("0");
      else if(ae.getSource()==dot)
            {
             if(((result.getText()).indexOf("."))==-1)
                result.setText(result.getText()+".");
           }
      else if(ae.getSource()==minus)
             {
             preRes=Double.parseDouble(result.getText());
             lastCommand="-";
             result.setText("0");
             }
      else if(ae.getSource()==div)
             {
             preRes=Double.parseDouble(result.getText());
             lastCommand="/";
             result.setText("0");
             }
      else if(ae.getSource()==equal)
             {
             secVal=Double.parseDouble(result.getText());
             if(lastCommand.equals("/"))
                  res=preRes/secVal;
             else if(lastCommand.equals("*"))
                  res=preRes*secVal;
             else if(lastCommand.equals("-"))
                  res=preRes-secVal;
             else if(lastCommand.equals("+"))
                  res=preRes+secVal;
             result.setText(" "+res);
             lastCommand="=";
             }
      else if(ae.getSource()==mul)
             {
              preRes=Double.parseDouble(result.getText());
              lastCommand="*";
              result.setText("0");
              }
      else if(ae.getSource()==plus)
              {
              preRes=Double.parseDouble(result.getText());
              lastCommand="+";
              result.setText("0");
              }

       }
 }

Answer 1

对于简单的小程序，应该这样做

• 扩展 JFrame（显然）

• 将东西从 init() 移到构造函数中。

  public class Calculator extends JFrame{
  
    public Calculator() {
    CalculatorPanel calc=new CalculatorPanel();
    getContentPane().add(calc);
    addWindowListener(new WindowAdapter() {
  
          public void windowClosing(WindowEvent e) {
              System.exit(0);
          }
      });
     pack();
     setVisible(true);
    }
  

  }

Answer 2

似乎没有人注意到您的 SSCCE 非常适合成为混合应用程序/小程序。这是因为主 GUI 被编码在 JPanel (CalculatorPanel) 中，然后可以添加到 JApplet 或 JFrame。

要创建混合，请将源代码的第一行更改为：

// <applet code='Calculator' width='400' height='450'></applet>
import javax.swing.*;
import javax.swing.JOptionPane;
import java.awt.*;
import java.awt.event.*;

public class Calculator extends JApplet {
   public void init() {
      CalculatorPanel calc=new CalculatorPanel();
      getContentPane().add(calc);
   }

   public static void main(String[] args) {
      Runnable r = new Runnable() {
         public void run() {
            JFrame f = new JFrame("Calculator");
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.add(new CalculatorPanel());
            f.pack();
            f.setLocationByPlatform(true);
            f.setVisible(true);
        }
      };
      SwingUtilities.invokeLater(r);
   }
}

然后，将其编译并作为小程序和应用程序运行，类似于..

prompt> javac Calculator.java
prompt> appletviewer Calculator.java  // run the applet
prompt> java Calculator               // run the application

Answer 3

不要太多

public class Calculator extends JFrame{   //1
   public void init() {
      CalculatorPanel calc=new CalculatorPanel();
      getContentPane().add(calc);
      this.show();       //2
      }
   }

当然还有一个主要功能...

Answer 4

糟糕的代码... ;-)

不管怎样，只要做一些简单的改变，它就可以工作：

public class Calculator
{
  public static void main(String[] args)
  {
    // Schedule a job for the event-dispatching thread:
    // creating and showing this application's GUI.
    SwingUtilities.invokeLater(new Runnable()
    {
      public void run()
      {
        JFrame calc = new JFrame();
        CalculatorPanel display = new CalculatorPanel();
        calc.add(display);
        calc.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        calc.pack();
        calc.setVisible(true);
      }
    });
  }

  static class CalculatorPanel extends JPanel implements ActionListener 
  {
    // ...
  }
}

Answer 5

一种方法是通过以下方式将 JApplet 添加到 JFrame：

    JFrame f=new JFrame();
    f.setSize(x, y);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);

    Calculator calculator=new Calculator();
    calculator.setSize(x, y);

    f.add(calculator);

编辑：

Here 是它的教程。